Plate type heat exchanger



Oct. 6, 1964 A. LYSHOLM PLATE TYPE HEAT EXCHANGER 2 Sheets-Sheet 1 Filed March 31, 1958 INVENTOR Z 75190.4?

ATTORNEYS Oct. 6, 1964 A. LYSHOLM Filed March 31, 1958 fiA F A ySflOL/V ATTORNEYS United States Patent 3,151,675 PLATE TYPE HEAT EXCHANGER Alf Lyslrolm, Karlaplan 11, Stockholm, Sweden Filed Mar. 31, 1958, Ser. No. 725,144 Claims priority, application Sweden, Apr. 2, 1957 Claims. (Cl. 165-166) This invention relates to a heat exchanger. It is a well known fact that the transfer of heat between a fluid in motion and a surface is dependent on the thickness of the boundary layer extending along the surface. If this thickness is reduced or the boundary layer is removed as much as possible, the transfer of heat will be considerably improved.

The invention is based on the above consideration and its main object is to improve the transfer of heat between a fluid in motion and a surface by providing for disturbances of flow in the passage for the fluid such as locally to remove or thin the boundary layer. However, since such disturbances cause an increase of the resistance to flow, the improved transfer of heat is often balanced by the increase in the flow losses.

More specifically, the object of the invention is to provide a heat exchanger having one or more passages for a heat emitting or heat absorbing fluid in motion, in which the above inconvenience is eliminated due to the fact that each passage has restricted portions spaced apart along the passage. Still more specifically, the arrangement should be one wherein the following relation holds for the ratio In of the smallest to the largest crosssectional area of each passage and the ratio of the distance L between the restricted portions to the hydraulic diameter D of the passage, namely,

wherein the factor K has a value of between 4 and 20, dependent upon the use for which the heat exchanger is to be constructed. If for a certain use it is desired to secure an efiicient heat transmission while maintaining a comparatively low resistance to flow, the value of the factor K should be between and 20. This holds true in cases where the dimensions of the heat exchanger are of minor importance. If the value of the factor K is reduced to between 6 and 10, the heat exchanger will obtain smaller dimensions as a result of the improved transfer of heat, whereas the resistance to flow is somewhat increased, but is still lying within reasonable limits. Finally, there may be cases in which it is desired to avoid too great variations of the heat transfer along the passage in order to prevent local overheating. In such cases, the value of the factor K should lie between 4 and 6. Such a heat exchanger will obtain comparatively small dimensions as a result of a very effective heat transmission.

The invention is explained more fully hereinbelow with reference to the drawings in which:

FIGURE 1 is a longitudinal sectional view of a passage for a heat exchanger;

FIGURE 2 is a top view, partly broken away, of an element for a heat exchanger according to the invention;

FIGURE 3 is a sectional view of the element taken on the line 3-3 of FIGURE 2;

FIGURE 4 is a sectional view of the element taken on the line 4-4 of FIGURE 2;

FIGURE 5 is a top view of a modified heat exchanger plate; and

FIGURE 6 is a sectional View of the modified plate taken on the line 6--6 of FIGURE 5.

The passage shown in FIGURE 1 is formed between two plates 1 and 2. The last named plate has furrows 3 extending at right angles to the direction of flow indi- "ice cated by an arrow, such as to obtain a varying crosssectional area of the passage. The restricted portions 4 alternate with portions 5 having constant cross-sectional areas. If, by way of example, the distance between the plates 1 and 2 at the restricted portions 4 amounts to 10 millimetres and at the portions 5 amounts to 15 millimetres, the ratio m of the smallest to the largest cross-sectional area will be equal to 0.67. The equivalent diameter is about 30 millimetres. If the distance between adjacent restricted portions is assumed to be 120 millimetres, the ratio of said distance L to the equivalent or hydraulic diameter D will be equal to 4. It has been proved that under these conditions the transfer of heat from the fluid flowing through the passage between the plates 1 and 2 is very satisfactory and that the resistance to flow is comparatively low.

In accordance with a preferred form of the invention, the passage should be devised such that the above named dimensions satisfy the equation wherein the value of the factor K is between 4 and 20.

In the above example of dimensions the factor K amounts to about 7. If the factor K is between 4 and 6, the resistance to flow will be comparatively high, but the coeflicient of heat transmission will vary only slightly along the length of the passage. If the value of the factor K is between 6 and 10, the coeflicient of heat transmission will still be high, but the resistance to flow will be lower. If the value of the factor is between 10 and 20, the resistance to flow will be rather low, while the coefiicient of heat transmission will be considerably higher than for a passage having a constant cross-sectional area. The ratio m of the smallest to the largest cross-sectional area should be between 0.4:1 and 0.911.

As will be seen from FIGURE 1, diffuser-shaped portions are provided in front of as well as behind the smallest cross-sectional area of the restricted portions, the result being a reduction of the flow losses. It has proved that the succeeding difluser-shaped portion is highly important, whereas a comparatively abrupt transition may be permitted at the upstream side between the largest and the smallest cross-sectional areas.

The furrows 3 which cause the restricted portions may be located at an angle with respect to the direction of flow, said angle amounting to between 25 and and preferably between 60 and 90.

FIGURES 2 to 4 illustrate part of a heat exchanger built up by plates in accordance with the invention. In this case, the furrows 3 of the plates 2 project in opposite directions and are separated by flat portions 3a. There are no plane plates in this embodiment. Restricted portions 4 alternate with portions having constant crosssectional areas 5 and portions having enlarged crosssectional areas 6. The plates 2 bear against spacing plates 7 which have oppositely projecting ridges 8 extending in the direction of flow and abutting against the inwardly projecting furrows 3 of the plates 2. The ridges 8 are separated by flat portions 8a. Thus, fluid flow channels are formed between adjacent plates, each channel having side walls formed by confronting plate portions 3a and 8a and each channel having lateral walls formed in part by the ridges 8 and in part by those portions of the furrows 3 which are immediately adjacent the ridges 8.

From FIGURE 2 it will be seen that the furrows 3 of the plates 2 extend obliquely With respect to the direction of flow of the fluid indicated by an arrow, whereas the ridges S of the plates 7 are parallel to the direction of flow. In the modification shown in FIGURES 5 and 6 a spacing plate 7 having parallel spacing ridges 8' is illustrated which has in addition flow-restricting furrows 9. The furrows 9 extend obliquely between the ridges 8' and are somewhat lower than the furrows 3 of the plates 2 in FIGURES 24 a p The invention is not limited 'to the above described and illustrated embodiments which may be modified within the scope of the appending claims.

What I claim is: Y I

1. A heat exchange plate structure comprising a pack of spaced, opposed plates, each of said plates being in contact with adjacent plates at least partially along parallel spacing ridges which are integral with and project from one of the plates, the spaces between adjacent plates forming a plurality of parallel straight channels for flow of gaseous heat exchanging fluid between adjacent plates, each of said channels having spaced side walls'formed by confronting portions of adjacent plates and lateral walls formed at least. partially by adjacent ridges and the width of said side walls being several times that of said lateral walls, and a plurality of furrows extending obliquely across and integral with at least one of the confronting portions which form said side walls of each of said channels, saidfurrows being relatively narrow and shallow as compared with/the width and depth of said channels and said furrows being separated by intervening plane side wall surfaces each several times the width of the. adjacent furrows.

7 2. A heat exchanger element for gaseous media comprising a pack of plates forming passages for gas flow on b oih sidesof each plate, said pack being composed of spacing plates having integral parallel ridges extending in the main direction of the gas flow and projecting on both sides of each plate, said ridges being separated by fiat plate portions, said spacing plates alternating with intermediate plates and engaging the same along said ridges, said intermediate plates having integral parallel furrows projecting transversely to said main direction of flow on both sides of each plate and extending at an'angle to said main direction of flow, said furrows being sepa rated by flat plate portions extending in the main direction of flow, the length of said flat plate portions between said furrows when measured in said direction being larger than the distance between adjacent plates.

3. A heat exchanger element as claimed in claim 1, wherein the furrows are straight and extend over the whole distance between adjacent ridges of the spacing plates.

4. A heat exchanger element as claimed in claim 1, wherein spaced parallel oblique furrows are alsoprovided in the fiat plate portions between the ridges of the spacing plates. V V

5. A heat exchanger'element as claimed in claim 4, wherein the furrows of thespacing plates are lower than the furrows of the intermediate plates.

References Cited in the file of this patent UNITED STATES PATENTS. f V V 1931 1,823,481 Zander Sept. 15, 7 1,991,555 Holmes Feb.'19, 1935 2,017,201 Bossart et al. Oct. 15, 1935 2,023,965; Lysholm Dec. 10, 1935 2,596,642 Boestad May 13, 1952 2,696,976 Boestad et a1. Dec. 14, 1954 2,737,446 Ljungstrom Apr. 2, 1957 2,940,736 Odn an June 14, 1960 V FOREIGN PATENTS 359,276 France Jan. 16, 1906 679,285 Germany Aug. 2, 1939 209,993 Great Britain Jan. 24, 1924 684,602 Great Britain Dec; 24, 1952 Great Britain Jan;.'13, 1954 OTHER REFERENCES V Bulletin No. 633, The Air Preheater Corp., June 1933. 

1. A HEAT EXCHANGE PLATE STRUCTURE COMPRISING A PACK OF SPACED, OPPOSED PLATES, EACH OF SAID PLATES BEING IN CONTACT WITH ADJACENT PLATES AT LEAST PARTIALLY ALONG PARALLEL SPACING RIDGES WHICH ARE INTEGRAL WITH AND PROJECT FROM ONE OF THE PLATES, THE SPACES BETWEEN ADJACENT PLATES FORMING A PLURALITY OF PARALLEL STRAIGHT CHANNELS FOR FLOW OF GASEOUS HEAT EXCHANGING FLUID BETWEEN ADJACENT PLATES, EACH OF SAID CHANNELS HAVING SPACED SIDE WALLS FORMED BY CONFRONTING PORTIONS OF ADJACENT PLATES AND LATERAL WALLS FORMED AT LEAST PARTIALLY BY ADJACENT RIDGES AND THE WIDTH OF SAID SIDE WALLS BEING SEVERAL TIMES THAT OF SAID LATERAL WALLS, AND A PLURALITY OF FURROWS EXTENDING OBLIQUELY ACROSS AND INTEGRAL WITH AT LEAST ONE OF THE CONFRONTING PORTIONS WHICH FORM SAID SIDE WALLS OF 